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Geomechanics and Engineering
  Volume 8, Number 6, June 2015, pages 783-799

In situ horizontal stress effect on plastic zone around circular underground openings excavated in elastic zones
Eren Komurlu, Ayhan Kesimal and Rohala Hasanpour

    In this study, effect of horizontal in situ stress on failure mechanism around underground openings excavated in isotropic, elastic rock zones is investigated. For estimating the plastic zone occurrence, an induced stress influence area approach (Bray Equations) was modified to define critical stress ratio according to the Mohr-Coulomb failure criterion. Results obtained from modified calculations were compared with results of some other analytical solutions for plastic zone thickness estimation and the numerical modelling (finite difference method software, FLAC2D) study. Plastic zone and its geometry around tunnels were analyzed for different in situ stress conditions. The modified equations gave similar results with those obtained from the other approaches. However, safer results were calculated using the modified equations for high in situ stress conditions and excessive ratio of horizontal to vertical in situ stresses. As the outcome of this study, the modified equations are suggested to use for estimating the plastic zone occurrence and its thickness around the tunnels with circular cross-section.
Key Words
    horizontal in situ stress; plastic zone; tunnel stability; stress distribution around tunnels
(1) Eren Komurlu, Ayhan Kesimal:
Department of Mining Engineering, Karadeniz Technical University, Trabzon, Turkey;
(2) Rohala Hasanpour:
Department of Mining Engineering, Hacettepe University, Beytepe, Ankara, Turkey.

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